> ## Documentation Index
> Fetch the complete documentation index at: https://docs.asksurf.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Category Metrics



## OpenAPI

````yaml openapi.json GET /gateway/v1/prediction-market/category-metrics
openapi: 3.1.0
info:
  title: Hermod
  version: 0.0.1
servers:
  - url: https://api.asksurf.ai
security: []
paths:
  /gateway/v1/prediction-market/category-metrics:
    get:
      tags:
        - Prediction Market
      summary: Prediction Market Category Metrics
      description: >-
        Returns daily notional volume and open interest aggregated by category
        across Kalshi and Polymarket.


        **Filters:** `source` or `category`.


        **Data refresh:** daily
      operationId: prediction-market-category-metrics
      parameters:
        - description: 'Filter by prediction market platform: `Kalshi` or `Polymarket`'
          explode: false
          in: query
          name: source
          schema:
            description: 'Filter by prediction market platform: `Kalshi` or `Polymarket`'
            enum:
              - Kalshi
              - Polymarket
            examples:
              - Polymarket
            type: string
        - description: Filter by top-level category
          explode: false
          in: query
          name: category
          schema:
            description: Filter by top-level category
            enum:
              - crypto
              - culture
              - economics
              - financials
              - politics
              - stem
              - sports
            examples:
              - politics
            type: string
        - description: 'Predefined time range: `7d`, `30d`, `90d`, `180d`, `1y`, or `all`'
          explode: false
          in: query
          name: time_range
          schema:
            default: 30d
            description: 'Predefined time range: `7d`, `30d`, `90d`, `180d`, `1y`, or `all`'
            enum:
              - 7d
              - 30d
              - 90d
              - 180d
              - 1y
              - all
            examples:
              - 30d
            type: string
        - description: Maximum rows to return
          explode: false
          in: query
          name: limit
          schema:
            default: 200
            description: Maximum rows to return
            examples:
              - 200
            format: int64
            maximum: 10000
            minimum: 1
            type: integer
        - description: Pagination offset
          explode: false
          in: query
          name: offset
          schema:
            default: 0
            description: Pagination offset
            examples:
              - 0
            format: int64
            minimum: 0
            type: integer
      responses:
        '200':
          content:
            application/json:
              schema:
                $ref: >-
                  #/components/schemas/DataResponsePredictionMarketCategoryMetricsItem
          description: OK
        default:
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/DataAPIError'
          description: Error
      security:
        - AccessToken: []
components:
  schemas:
    DataResponsePredictionMarketCategoryMetricsItem:
      additionalProperties: false
      properties:
        $schema:
          description: A URL to the JSON Schema for this object.
          examples:
            - >-
              https://example.com/schemas/DataResponsePredictionMarketCategoryMetricsItem.json
          format: uri
          readOnly: true
          type: string
        data:
          items:
            $ref: '#/components/schemas/PredictionMarketCategoryMetricsItem'
          type:
            - array
            - 'null'
        meta:
          $ref: '#/components/schemas/OffsetMeta'
      required:
        - data
        - meta
      type: object
    DataAPIError:
      additionalProperties: false
      properties:
        $schema:
          description: A URL to the JSON Schema for this object.
          examples:
            - https://example.com/schemas/DataAPIError.json
          format: uri
          readOnly: true
          type: string
        error:
          $ref: '#/components/schemas/DataAPIErrorDetail'
      required:
        - error
      type: object
    PredictionMarketCategoryMetricsItem:
      additionalProperties: false
      properties:
        category:
          description: Top-level category
          type: string
        notional_volume_usd:
          description: Notional trading volume in USD
          format: double
          type: number
        open_interest_usd:
          description: Open interest in USD
          format: double
          type: number
        source:
          description: 'Prediction market platform: Kalshi or Polymarket'
          type: string
        subcategory:
          description: Subcategory within the category
          type: string
        timestamp:
          description: Unix timestamp in seconds (midnight UTC for the trading day)
          format: int64
          type: integer
      required:
        - timestamp
        - source
        - category
        - subcategory
        - notional_volume_usd
        - open_interest_usd
      type: object
    OffsetMeta:
      additionalProperties: false
      properties:
        cached:
          description: Whether this response was served from cache
          type: boolean
        credits_used:
          description: Credits deducted for this request
          format: int64
          type: integer
        limit:
          description: Maximum number of items returned in this response
          format: int64
          type: integer
        offset:
          description: Number of items skipped (pagination offset)
          format: int64
          type: integer
        total:
          description: >-
            Total number of matching items (before pagination). Omitted when
            total is unknown.
          format: int64
          type: integer
      required:
        - limit
        - offset
        - credits_used
        - cached
      type: object
    DataAPIErrorDetail:
      additionalProperties: false
      properties:
        code:
          type: string
        message:
          type: string
      required:
        - code
        - message
      type: object

````